This invention of the parent application relates to filtering apparatus for separating solid or liquid (aerosols) particulate from carrier fluids such as the flue or fuel gas streams derived from combustion or gasification and other like processes. The invention of the parent application concerns itself with filtering apparatus in power plants and other facilities such as industrial and municipal incinerators in which the separation of particulate is effected by ceramic so-called "candle filters." The so-called "candle filters" are hollow ceramic porous filter tubes and will be sometimes referred to in this application as filter tubes. "Candle filters" are currently available from such organizations as Schumacher of Crailsheim, West Germany, Didier, Eisenberg, West Germany, Refracton, Rochester, N.Y. and Coors, Golden, CO., U.S.A. A typical candle filter is 2.36-inches (60 mm) in outside diameter and 1.57-inches (40 mm) inside diameter below and the head and up to 4.92-feet (1.5 meters) in length. The gas to be cleaned flows across the outside of the filter and the cleaned gas flows through the inside of the filter. The bottom of the "candle filter" is sealed.
It is essential that each filter tube is mounted so that it performs effectively its filtering function in the gas being processed, which is at a high temperature and under high pressure. Typically, the mounting includes a metal housing in which each filter tube is suspended in filtering relationship with the gas which is processed. It is necessary that the differential thermal expansion between the metal housing and the ceramic tube, which occurs at the high temperature of the gas being processed, be taken up. It is also necessary that the penetration of the separated particulate between the filter tube and the housing be suppressed. The filter tube must be securely mounted and centered in the housing so that it does not become disengaged from the housing under the pressure of the gas. Displacement of the tube during operation and eccentric loading of the tube must be avoided. Asperities in the ceramic tube in regions where it interfaces with the housing must be filled to the extent practicable.
It is an object of this invention to provide a filter assembly which meets the above-listed requirements.